1. Technical Field
This invention relates generally to gas turbine engines and particularly to a gas turbine engine rotor seal.
2. Background Information
Gas turbine engines such as those that power aircraft and industrial equipment employ a compressor to compress air which is drawn into the engine and a turbine to capture energy associated with the combustion of a fuel air mixture which is exhausted from the engine's combustor. The compressor and turbine employ rotors which typically comprise a multiplicity of airfoil blades mounted on or formed integrally into the rims of a plurality of disks. The compressor disks and blades are rotationally driven by rotation of the engine's turbine. It is a well-known practice to arrange the disks in a longitudinally axial stack in compressive inter-engagement with one another, which is maintained by a tie shaft which runs through axially aligned central bores in the disks. The disks are exposed to working fluid flowing through the engine and therefore, are exposed to extreme heating from such working fluid. For example, in a gas turbine engine high pressure compressor, the disks are exposed to highly compressed air at highly elevated temperatures. This exposure of the disks to such elevated temperatures combined with repeated acceleration and deceleration of the disks resulting from the normal operation of the gas turbine engine at varying speeds and thrust levels may cause the disks to experience low cycle fatigue, creep and possibly cracking or other structural damage especially at the aft end of the compressor disk stack where the temperature and pressure of air flowing through the compressor are highest.
It is a common practice to seal the stator of a gas turbine engine to a rotor thereof to control the flow of working fluid through the engine. For example, it is a known practice to seal the radially inner ends of flow directing vanes in the stator to the engine's rotor to prevent working fluid flowing through the engine from flowing inwardly around the radially inner ends of the vanes and thereby bypassing the flow directing airfoil surfaces of such vanes. Accordingly, it is well-known to provide rotating seal elements such as knife edge seals mounted on the rotor disks which seal to stationary seal elements such as honeycomb or equivalent stationary seal elements mounted on the ends of the stator vanes. The aforementioned low cycle fatigue and creep collectively referred to as thermal mechanical fatigue experienced by disks as noted hereinabove is particularly troublesome with respect to the knife edge seals mounted on disks due to the discontinuities inherent in the mounting of the knife edge seals on the disks. Such discontinuities in the disks associated with the knife edge seals mounted thereon result in high mechanical stress concentrations at the knife edge seals which intensify the risks of damage thereto resulting from the aforementioned thermal mechanical fatigue. Therefore, it will be appreciated that such disk mounted knife edge seals must be periodically removed for normal maintenance involving the repair and/or replacement thereof to maintain the operational efficiency of the engine. It will be appreciated that maintenance repair and/or replacement of knife edge seals mounted on or integral with rotor disks involves the disassembly of the disks from the rotor tieshaft, an expensive and time consuming maintenance procedure.
Therefore, it will be appreciated that a gas turbine engine rotary seal which is less susceptible to thermal mechanical fatigue than prior art disk mounted seals and more easily accessed for repair and maintenance of the seals would be highly desirable.